Question

4g of a divalent metal was dissolved in 100cc of 2M H2SO4 (f=1.01). The excess acid required 30cc of 1N NaOH for complete neutralization. Find the atomic mass of the metal.

A. 60 g/mol
B. 40 g/mol
C. 30 g/mol
D. 20 g/mol

Answer 1

The calculation of the atomic mass of a divalent metal through titration showed a result of approximately 23.53 g/mol, which does not match the given options. A reassessment of the valency or reaction stoichiometry might be required.

Step-by-step explanation:

The question involves calculating the atomic mass of a divalent metal using a titration process where the metal is reacted with sulfuric acid (H2SO4), and the excess acid is titrated with sodium hydroxide (NaOH).

Firstly, we find the moles of H2SO4 that reacted with NaOH:

• 30 cc (0.03 L) of 1N NaOH is used.
• Moles of NaOH = Volume (in L) × Normality = 0.03 × 1 = 0.03 moles.
• Since the reaction between NaOH and H2SO4 is 1:1, moles of excess H2SO4 = 0.03 moles.

Next, we calculate the moles of H2SO4 initially present:

• 100 cc (0.1 L) of 2M H2SO4 = 0.1 × 2 = 0.2 moles.
• Moles of H2SO4 that reacted with the metal = Total H2SO4 - Excess H2SO4 = 0.2 - 0.03 = 0.17 moles.

Since the metal is divalent, it reacts with H2SO4 in a 1:1 ratio, we can say:

• Moles of metal = Moles of H2SO4 = 0.17 moles.
• Atomic mass of the metal = Mass / Moles = 4 g / 0.17 moles ≈ 23.53 g/mol.

However, this does not match any of the provided options A-D, suggesting there might be a mistake in the question or the options given. If we reconsider the valency of the metal or the stoichiometry of the reaction, we might get a different result that fits one of the options.